日本金属学会誌

J. Japan Inst. Metals, Vol. 49, No. 3 (1985),
pp. 187-195

The Characteristics of Low Temperature Deformation in Commercial Tungsten Wires

Koji Tanoue1, Kanji Yahiro2, Hisatoshi Mori3 and Hidehiko Matsuda1

1Department of Metal Processing Engineering, Kyushu Institute of Technology, Kitakyushu
2Graduate Student, Kyushu Institute of Technology, Kitakyushu. Present address: Kyushu Matsushita Electric Co., Ltd., Tamana
3Nippon Tungsten Co., Ltd., Iizuka

Abstract:

Temperature (77--500 K) and strain rate (3×10-6--10-2 s-1) dependence of the yield and the flow stresses of powder metallurgical tungsten wires are mainly investigated. The former is marked and can be experimentally represented by Guyot and Dorn's equation, σ∝σ p[1-(T/T0)1/2] based on the Peierls mechanism. The latter is estimated exclusively from stress relaxation tests. The shape of stress relaxation curves plotted as log σ vs. log \dotεp is straight at any strain and temperature, giving a strain rate sensitivity parameter m[=(∂ ln σ/∂ ln \dotεp)T,ε] from its slope. The strain independent mean values of m are obtained to be 0.01--0.03 with a maximum at 300 K. These m values imply that the yield and the flow stresses do not so strongly depend on strain rate.
The variation of the Gibbs free energy Δ G with stress can be expressed by Δ G=A-B ln σ , assuming that the plastic strain rate during stress relaxation is given by the Arrhenius type equation. It becomes evident from the parameter B dependent on temperature that the short range obstacle profile for dislocation movement depends on temperature. Accordingly, the good arrangement of stress for temperature with Guyot and Dorn's equation may be due to the apparent satisfaction of the present results with a profile derived from their model.


(Received 1984/11/5)

Keywords:

powder metallurgy, fiber structure, low temperature deformation, stress relaxation, fractography, tungsten wires


PDF(Free)PDF (Free)     Table of ContentsTable of Contents

Please do not copy without permission.